[Release] Update versions for 12.6.0 (#15458)

FirebaseAppDistribution.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = 'FirebaseAppDistribution'
-  s.version          = '12.5.0-beta'
+  s.version          = '12.6.0-beta'
   s.summary          = 'App Distribution for Firebase iOS SDK.'
 
   s.description      = <<-DESC
@@ -30,10 +30,10 @@ iOS SDK for App Distribution for Firebase.
   ]
   s.public_header_files = base_dir + 'Public/FirebaseAppDistribution/*.h'
 
-  s.dependency 'FirebaseCore', '~> 12.5.0'
+  s.dependency 'FirebaseCore', '~> 12.6.0'
   s.dependency 'GoogleUtilities/AppDelegateSwizzler', '~> 8.1'
   s.dependency 'GoogleUtilities/UserDefaults', '~> 8.1'
-  s.dependency 'FirebaseInstallations', '~> 12.5.0'
+  s.dependency 'FirebaseInstallations', '~> 12.6.0'
 
   s.pod_target_xcconfig = {
     'HEADER_SEARCH_PATHS' => '"${PODS_TARGET_SRCROOT}"'